How to list strips in Blender VSE?
Select all of your strips you want to put in order and run this script:

import bpy

strips = bpy.context.selected_editable_sequences
strips = sorted(strips, key=lambda strip: strip.frame_final_start)

cleanup = []
for i in range(1, len(strips)):
    st0 = strips[i-1]
    st1 = strips[i]
    cleanup.append( [ st1, st1.channel ])
    st1.frame_start = st0.frame_start + st0.frame_final_duration
for x in cleanup:
    x[0].channel = 1
strips[0].channel = 1



It's a version of this script: VSE script for to add constant gaps between strips?